The present invention relates to a signal synchronizing system and in particular to a synchronizing system useful for time base correction systems.
Time base correcting synchronizing systems are generally applicable where it is desirable to derive timing signals from a source of signals such as television signals which have been recorded on a magnetic medium.
When a recorded medium, for example, in the form of magnetic tape, is replayed it is common to find that the recovered signal includes time base variations due, for example, to mechanical limitations of the recording and playback mechanism of the recorder as well as variations in the medium itself. If left uncorrected these time base variations will produce picture defects in the reproduced image which may range from objectionable color reproduction to a complete breakup of the image scanning raster.
In general time base errors are corrected by writing the incoming television signal into a storage medium at a time rate which varies with the time base errors (jitter) accompanying the incoming signal. Once stored the television signal is read out of storage at a time rate determined by a stable local reference. A time base corrector of this general description is described in detail in co-pending application Ser. No. 604,775 of A.C. Dischert, Jr., et al. entitled SIGNAL PROCESSOR USING CHARGE-COUPLED DEVICES assigned to the same assignee and filed concurrently herewith.
In time base correctors which are to be utilized with color television signals it is not satisfactory to vary the write-in time rate only in accordance with the time error of the leading edge of the incoming synchronizing component of the horizontal line rate. This is because the color reference component, burst, which occurs during the horizontal blanking interval of each television line is not time-defined in terms of the leading edge of the horizontal synchronizing component. Therefore it is necessary when processing color television signals which require time base correction to accurately determine the burst crossovers or phasing with respect to the leading edge of the horizontal synchronizing components.